Acetylcholinesterase inhibitory activity of didehydrostemofoline, stemofoline alkaloids and extracts from Stemona collinsiae Craib roots

Introduction: Acetylcholinesterase (AChE) inhibition is one of insect toxicity mechanisms found in many plants. Stemona collinsiae Craib, a traditional insecticidal plant, has been of interest for its AChE inhibitory activity. Methods: Powdered roots of S. collinsiae were successively extracted with hexane, dichloromethane, and methanol. The contents of major active insecticidal components, didehydrostemofoline and stemofoline alkaloids, were analyzed by HPLC. Anti-AChE activity was evaluated using Ellman’s colorimetric method and TLC-bioautography. Results: The contents of didehydrostemofoline and stemofoline alkaloids in the hexane, dichloromethane, and methanol extracts were 3.59 and 0.18, 40.78 and 0.74, and 1.43 and 0.09% w/w, respectively. TLC fingerprints of each extract showed major spots of didehydrostemofoline and stemofoline of which TLC bioassays indicated active AChE inhibitory activity. IC₅₀ values on anti-AChE activities of hexane, dichloromethane and methanol extracts were 126.72, 73.78, and >1000 mg/ml, respectively while those of didehydrostemofoline, stemofoline, and standard galanthamine were 131.3, 102.1, and 1.30 mM, respectively. Conclusion: The AChE inhibitory activity of hexane, dichloromethane and methanol extracts from S. collinsiae roots and their major alkaloids, didehydrostemofoline and stemofoline, were determined. The data support the traditional utilization of this plant as a natural insecticide.

Key words: Acetylcholinesterase inhibition, Didehydrostemofoline, Stemofoline, Stemona collinsiae, Stemonaceae.